The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
In the construction and development of wells formed in subterranean formations, such as wells for the production of oil and gas, various operations are carried out that require the introduction of fluids of different types into the wellbore and/or into formation surrounding the wellbore.
During drilling of the well, for example, drilling muds or fluids are typically circulated through the drill string, through the drill bit at the end of the drill string and up through the annulus between the drilled wellbore and drill string. The circulated drilling fluid is used to carry formation rock present as cuttings or drilled solids that are removed from the wellbore as the drilling fluid is circulated back to the surface. After drilling is complete, a cement composition may be used to cement a casing or liner within the wellbore. Oftentimes, the drilling fluid is removed from the wellbore by the introduction of the cement into the wellbore. Poor liquid-liquid interface stability between the drilling fluid and the cement, however, may result in improper displacement of the drilling fluid by the cement, which may be characterized by non-uniform and/or incomplete cementing or the formation of cement fingers, which may lead to failures in zonal isolation, microannulus formation, etc.
Hydraulic fracturing is another operation conducted in wells that is used to increase the production of fluids from the subterranean formations. Hydraulic fracturing involves introducing fluids into the wellbore at very high flow rates and pressures to facilitate cracking and fracturing of the surrounding formation. In hydraulic fracturing, typically a proppant is introduced into the formation with the fracturing fluids at certain stages of the fracturing operation. The proppant (e.g. sand) is deposited in the formed fractures of the formation so the proppant prevents the fracture from closing when the pressure is reduced. This allows fluids to flow from the formation through the fractures to the wellbore so that they can be produced. Various methods exist for fracturing such formations. In one technique, the fracturing operation is carried out using multiple proppant slugs or pulses to provide heterogeneous placement of the proppant. This is accomplished by introducing alternating stages of proppant-laden fluids and proppant-free fluids so that multiple clusters of proppant are provided within the fractures of the formation. In such treatments, separate and concentrated proppant clusters are desired. Poor liquid-liquid interface stability between the proppant-laden slugs and proppant-free slugs may result in dispersion of the proppant, thus inhibiting effective placement of proppant clusters.
In downhole operations where fluids having different natures or characteristics are sequentially introduced, stabilization of the liquid-liquid interface between the fluids may be important to provide a successful treatment or operation. The present invention is directed to facilitating the stabilization of the liquid-liquid interface between such fluids.